This invention relates generally to a heat and pressure fuser for an electrophotographic printing machine, and more particularly the invention is directed to a fuser roll structure that minimizes the effects of paper edge contact with an elastomeric surface.
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to selectively dissipate the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet.
In order to fix or fuse the toner material onto a support member permanently by heat, it is necessary to elevate the temperature of the toner material to a point at which constituents of the toner material coalesce and become tacky. This action causes the toner to flow to some extent onto the fibers or pores of the support members or otherwise upon the surfaces thereof. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be bonded firmly to the support member.
One approach to thermal fusing of toner material images onto the supporting substrate has been to pass the substrate with the unfused toner images thereon between a pair of opposed roller members at least one of which is internally heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the heated fuser roll to thereby effect heating of the toner images within the nip.
The heated fuser roll which is usually the roll that contacts the toner images on a substrate such as plain paper. In any event, the roll contacting the toner images must be provided with an abhesive material for preventing toner offset to the fuser member. Two materials which are commonly used for such purposes are Viton and silicone rubber.
Viton fuser rolls are susceptible to chemical degradation and hardening due to DDAMS and CPC in the toner. Silicone rubber does not have a similar problem. If a silicone material is used as the coating on the fuser roll its release and copy quality characteristics last a long time. However, paper path edge wear limits the useful life of rolls covered with silicone rubber. This is particularly true in machines that have more effective paper edge registration. Thus, paper edge wear varies appreciably from machine to machine depending upon the performance of the paper edge registration mechanism. As an example, it was found that in one machine using a silicone coated fuser roll that it was possible to fuse a million copies before the useful life of the fuser roll was exceeded. In another machine, edge wear limited useful life of the fuser roll to one hundred thousand copies.
Following is a discussion of prior art, incorporated herein by reference, which may bear on the patentability of the present invention. In addition to possibly having some relevance to the question of patentability, these references, together with the detailed description to follow, may provide a better understanding and appreciation of the present invention.
U.S. Pat. No. 5,281,506 granted on Jan. 25, 1994 discloses a method of making a fuser member having a polyorganosiloxane grafted onto a fluoroelastomer and method of fusing. A fuser member comprising a supporting substrate having an outer layer of a cured fluoroelastomer and having a thin surface layer of a polyorganosiloxane having been grafted to the surface of said cured fluoroelastomer in the presence of a dehydrofluorination agent for the fluoroelastomer and from a polyorganosiloxane having reactive functionality.
U.S. Pat. No. 5,219,612 issued on Jun. 15, 1993 discloses a method of using multilayered member for fusing thermoplastic resin toner images to a substrate in a fuser system of the type wherein a polymeric release agent having functional groups is applied to the surface of the fuser member. The multilayered fuser member has in sequential order a base support member, an abhesive layer comprising a copolymer of vinylidene fluoride and hexafluoropropylene and at least 20% by weight of the abhesive layer of a coupling agent comprising at least one organo functional silane and an activator, a tie coat layer of active ingredients comprising a copolymer of vinylidene fluoride and hexafluoropropylene and an outer elastomeric fusing surface comprising a copolymer of vinylidene fluoride and hexafluoropropylene and containing a metal oxide present in an amount sufficient to interact with a polymeric release agent having functional groups to provide an interfacial barrier layer between said fusing surface and toner.
U.S. Pat. No. 5,217,837 issued on Jun. 8, 1993 discloses a multilayered fuser member for fusing thermoplastic resin toner images to a substrate in a fuser system of the type wherein a polymeric release agent having functional groups is applied to the surface of the fuser member, the fuser member has a base support member, a thermally conductive silicone elastomer layer, an amino silane primer layer, an abhesive layer and an elastomer fusing surface comprising poly(vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene) a metal oxide present in the fusing surface to interact with the polymeric release agent to provide an interfacial barrier layer between the fusing surface and the toner and substantially unreactive with the elastomer, the elastomer having been cured from a solvent solution with a nucleophilic curing agent soluble in the solution and in the presence of 4 parts by weight of inorganic base per 100 parts of polymer, the abhesive layer having been cured from a solvent solution of the above composition from which the fusing surface is cured and from about 5 to about 10% by weight of a coupling agent.
U.S. Pat. No. 5,166,031 issued on Nov. 24, 1992 discloses a fuser member comprising a supporting substrate having an outer layer of a volume grafted elastomer which is a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane, said volume graft having been formed by dehydrofluorination of said fluoroelastomer by a nucleophilic dehydrofluorinating agent, followed by addition polymerization by the addition of an alkene or alkyne functionally terminated polyorganosiloxane and a polymerization initiator.
U.S. Pat. No. 5,141,788 issued on Aug. 25, 1992 discloses a fuser member comprising a supporting substrate having an outer layer of a cured fluoroelastomer and having a thin surface layer of a polyorganosiloxane having been grafted to the surface of said cured fluoroelastomer in the presence of a dehydrofluorination agent for the fluoroelastomer and from a polyorganosiloxane having reactive functionality. The outer layer of a polyorganosiloxane unlike the invention disclosed herein is not a discrete or continuous layer.
U.S. Pat. No. 5,061,965 issued on Oct. 29, 1991 discloses a release agent donor member for a toner fixing system wherein a polymeric release agent having functional groups is applied to the surface of a fuser member has a base member, an intermediate conformable silicone elastomer layer and an elastomer release agent donor layer comprising poly(vinylidenefluoride-hexafluoropropylenetetrafluoroethylene) where the vinylidenefluoride is present in an amount less than 40 mole percent, a metal oxide present in an amount sufficient to interact with the polymeric release agent having functional groups to transport a sufficient amount of the polymeric release agent to provide an interfacial barrier layer between the fusing surface parts by weight of inorganic base per 100 parts of polymer, the inorganic base being effective to at least partially dehydrofluorinate the vinylidenefluoride.
U.S. Pat. No. 5,049,444 issued on Sep. 17, 1991 discloses a multilayered member for fusing thermoplastic resin toner images to a substrate in a fuser system of the type wherein a polymeric release agent having functional groups is applied to the surface of the fuser member. The multilayered fuser member has in sequential order a base support member, an abhesive layer comprising a copolymer of vinylidene fluoride and hexafluoropropylene and at least 20% by weight of the abhesive layer of a coupling agent comprising at least one organo functional silaneand an activator, a tie coat layer of active ingredients comprising a copolymer of vinylidene fluoride and hexafluoropropylene and an outer elastomeric fusing surface comprising a copolymer of vinylidene fluoride and hexafluoropropylene and containing a metal oxide present in an amount sufficient to interact with a polymeric release agent having functional groups to provide an interfacial barrier layer between said fusing surface and toner.
U.S. Pat. No. 5,017,432 issued on May 21, 1991 discloses a fuser member and fuser system of a type wherein a polymeric release agent having functional groups supplied to the surface of the fuser member has an elastomer fusing surface comprising poly(vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene) wherein the vinylidenefluoride is present in the amount less than 40 mole percent, a metal oxide is present in amounts sufficient to interact with the polymer release agent having functional groups to provide an interfacial barrier layer between the fusing surface and the toner and being substantially unreactive with the elastomer and wherein the elastomer is cured from a solvent solution thereof with a nucleophilic curing agent soluble in the solution and in the presence of less than 4 parts by weight of inorganic base per 100 parts by weight of polymer with the inorganic base being effective to at least partially dehydrofluorinate the vinylidenefluoride.
U.S. Pat. No. 4,257,699 issued on Mar. 24, 1981 discloses afuser member, fuser assembly and method of fusing or fixing thermoplastic resin powder images to a substrate in a fuser assembly of the type wherein a polymeric release agent having functional groups is applied to the surface of the fuser member is disclosed. The fuser member comprises a base member having at least two layers of elastomer thereon, at least the outer layer elastomer surface having a metal-containing filler therein. Exemplary of such a fuser member is an aluminum base member coated with a first layer of poly(vinylidene fluoride-hexafluoropropylene) copolymer optionally having a metal-containing filler, such as lead oxide, dispersed therein and at least a second layer of poly(vinylidene fluoride-hexafluoropropylene) copolymer having metal-containing filler, such as lead oxide, dispersed therein coated upon said first layer.
U.S. Pat. No. 4,078,286 issued on Mar. 14, 1978 discloses silicone rubber employed as an outer coating material on a fuser member and is applied to the base member by means of a novel construction which prevents the separation of the outer silicone rubber coating from the roll even when silicone oil is applied thereto. The fuser member comprises a base member, a layer of a heat-resistant resin formed on the base member and a layer of a silicone rubber formed on the heat-resistant resin layer, the silicone rubber being vulcanized after the formation of the layer of silicone rubber on the resin layer. A primer layer may be used between the heat-resistant resin layer and the silicone rubber layer.